Coating precursor and method for coating a substrate with a refractory layer

ABSTRACT

The purpose of the invention is a coating precursor comprising a silicone resin, a mineral filler and an organic solvent capable of dissolving the said resin and putting the said mineral filler into suspension, the said silicone resin and the said mineral filler being capable of chemically reacting so as to produce a solid layer on a substrate after the organic solvent has evaporated and a cohesive refractory layer after a calcination operation. Another purpose of the invention is a method for coating a given surface of a substrate with at least one refractory layer containing silicon in which the substrate is coated with a coating precursor according to the invention so as to form a green layer and a heat treatment is carried out to calcine the said green layer and to form a cohesive refractory layer. The invention is a means of obtaining a protective coating capable of resisting oxidising environments, liquid metal and solid or molten salt.

FIELD OF THE INVENTION

[0001] This invention relates to the protection of objects and materialsfor use in the metallurgical industry, and particularly the aluminiumindustry. In particular, it relates to protective coatings for the saidobjects and materials.

STATE OF THE ART

[0002] The objects and materials used in the aluminium industry arefrequently exposed to corrosive environments and subjected to hightemperatures and severe thermal constraints. Containers (such as ladlesand furnaces), ducts (such as troughs, injectors and casting nozzles)and tools and devices designed to handle and treat liquid aluminium(such as filters and rotors) must have good mechanical and chemicalstrength. In particular, the surfaces of these objects that are exposedto liquid aluminium must not dissolve in liquid aluminium norcontaminate it.

[0003] Although the strength of materials typically used in thealuminium industry is generally sufficient, there are some applicationsor conditions for which an even higher strength is required. This is thecase particularly when it is required to reduce the number of inclusionsper tonne of cast aluminium to almost zero.

[0004] Therefore, the applicant looked for means of handling, producing,treating and casting aluminium and liquid aluminium alloyssatisfactorily under the most demanding conditions and applications.

DESCRIPTION OF THE INVENTION

[0005] An object of the invention is a coating precursor to be used forthe formation of a protective layer on a substrate. The said precursorcomprises a silicone resin and a mineral filler capable of reactingchemically with the said resin so as to produce a cohesive refractorylayer after a calcination operation of the layer.

[0006] More precisely, an object of the invention is a coating precursorcomprising a silicone resin (or organosiloxane), a mineral filler and anorganic solvent capable of dissolving the said resin and putting thesaid mineral filler into suspension, the said silicone resin and thesaid mineral filler being capable of chemically reacting so as toproduce a solid layer on a substrate after the organic solvent hasevaporated and a cohesive refractory layer after a calcinationoperation.

[0007] The said precursor is preferably homogeneous.

[0008] The silicone resin is a polysiloxane preferably comprising aproportion of OH groups, such as a polymethylsiloxane, apolydimethylsiloxane, a polymethylsilsesquioxane, or a mixture thereof,comprising a proportion of OH groups substituted for methyl groups. Theapplicant has noted that the proportion of OH groups is preferablybetween about 0.5% and about 2%. If the proportion of OH groups is toolow, there will not be sufficient propension to form a solid layer afterthe solvent has evaporated and with good cohesiveness after calcination.A very high proportion of OH groups may make the polysiloxane difficultto produce at an acceptable cost. The silanol (Si—OH) groups arepreferably stable so that the resin can be stored. These OH groups maybe grafted to a polysiloxane by hydrolysis. The siloxanic patterns ofthe polysiloxane according to the invention are advantageously wholly orpartly trifunctional or quadrifunctional.

[0009] The organic solvent is typically an apolar solvent such as axylene or a toluene. The xylene may be a mixture of different types ofxylene, such as o and p.

[0010] The mineral filler is typically chosen from among metal borides,carbides, nitrides and oxides, or from among non-metal borides, carbidesand nitrides (such as boron nitrides) or a combination or a mixturethereof. The said mineral filler is advantageously chosen from amongmetal compounds such as metal oxides, metal carbides, metal borides andmetal nitrides, or a combination or a mixture thereof. The mineralfiller is preferably capable of chemically reacting with the siliconeresin so as to produce a solid layer after the organic solvent hasevaporated and a refractory layer with good cohesiveness aftercalcination of the said green layer. The mineral filler may be chosen asa function of the physicochemical characteristics expected from thecoating (such as wettability or non-wettability by a liquid metal).

[0011] The metal compound is advantageously alumina, ZrO₂, ZrB₂, TiB₂ orTiO₂ or a combination or a mixture thereof. The alumina is preferably areactive calcined alpha alumina called a technical alumina, with a verylow hydration ratio (typically less than 1%, or even less than 0.5%).

[0012] The mineral filler is preferably in the form of a fine powder,which can give a fluid precursor and a uniform coating. It is typicallyadded to the silicone resin/organic solvent mixture after a finegrinding operation. The size grading of the mineral filler powder istypically such that the size of the grains is between 0.05 μm and 50 μm.

[0013] The physical properties of the coating, such as its mechanicalproperties, can sometimes be adapted by adjusting the proportion of themineral filler and/or its size grading.

[0014] According to one preferred embodiment of the invention, theprecursor is typically in the form of a slurry or a slip. It istypically obtained by mixing the resin, the mineral filler and theorganic solvent.

[0015] In this embodiment, the proportion of silicone resin in theprecursor is typically between 5 and 30% by weight, and preferablybetween 7.5 and 20% by weight, to enable satisfactory ceramisation ofthe coating during calcination. Apart from the solvent, the proportionof silicone resin in the precursor is typically between 15 and 40% byweight.

[0016] The proportion of organic solvent in the precursor is thentypically between 7.5% and 60% by weight, and preferably between 15 and30% by weight. The solvent quantity is preferably such that all thesilicone resin is dissolved and the mineral filler can be put intosuspension in the solution obtained.

[0017] The proportion of the mineral filler in the precursor istypically between 30% and 75% by weight, and preferably between 45 and70% by weight. If the proportion is too low, the deposition will be toothin and consequently it will be necessary to deposit a large number oflayers in succession. If the proportion is too large, the precursor willbe difficult to spread.

[0018] According to another preferred embodiment of the invention, theprecursor is typically in the form of a paste.

[0019] In this embodiment, the proportion of silicone resin in theprecursor is then typically between 7.5 and 20% by weight, andpreferably between 10 and 17.5% by weight, to enable satisfactoryceramisation of the coating during calcination.

[0020] The proportion of organic solvent in the precursor is typicallybetween 2.5% and 10% by weight.

[0021] The proportion of mineral filler in the precursor is typicallybetween 70% and 95% by weight, and preferably between 75% and 90% byweight.

[0022] In this embodiment, the coating precursor advantageously includesan additive capable of reducing the viscosity of the precursor. The saidadditive typically comprises a dispersing agent such as stearic acid.The proportion of the said additive in the precursor is typically lessthan 2% by weight, and more typically between 0.1 and 1%.

[0023] The precursor is typically obtained by mixing the resin, themineral filler and the additive, and if necessary grinding the mixture.

[0024] Another object of the invention is a method for coating a givensurface of a substrate with at least one refractory layer containingsilicon wherein:

[0025] the substrate is coated with a coating precursor according to theinvention so as to form a green layer;

[0026] a heat treatment called calcination treatment is carried out toeliminate volatile materials, to calcine the said green layer and toform a cohesive refractory layer.

[0027] The applicant has observed that the method according to theinvention can give a strong thin layer bonding strongly to the substratethat has good resistance to liquid metal and that has good cohesiveness.

[0028] The coating precursor may be prepared in at least two operations:

[0029] a silicone resin is dissolved in an organic solvent so as toobtain a solution of silicone resin;

[0030] the mineral filler is added into the solution of silicone resinthus obtained.

[0031] The substrate may be coated (typically including the depositionand spreading of the said precursor on the substrate) by any knownmeans. For example, the coating may be deposited by brushing (typicallyusing a brush and/or a roller), by dipping, by atomisation or byspraying (typically using a spray gun). Brushing, dipping andatomisation are particularly adapted to the deposition of precursors inthe form of a slurry or slip. Spraying is particularly adapted to thedeposition of precursors in the form of a paste. The temperature of thesubstrate may possibly be increased above the ambient temperature beforecoating in order to facilitate the formation of a homogeneous depositand bonding of the deposition by melting of the resin.

[0032] The method according to the invention may also comprisecomplementary operations such as preparation of the parts of thesubstrate surface to be coated and/or drying of the green coating beforethe heat treatment. The said drying treatment serves in particular toevaporate the said organic solvent and, at least partially, to solidifythe green layer (so that the substrate can be handled without damagingthe layer). The preparation of the substrate surface typically includescleaning and/or degreasing (for example using acetone).

[0033] In some applications, it may be advantageous to use a coatingprecursor also containing a wetting agent capable of facilitating theformation of a thin layer. This is the case particularly for some screenfilters for which it is required to coat the wires of the metal meshwithout blocking the openings. The said wetting agent is preferably asilane polyether, which encourages spreading of the coating on thesubstrate without preventing ceramisation of the refractory coatingduring the heat treatment. The chemical formula of the said silanepolyether is typically:

[0034] where R is an alkyl group and typically a methyl.

[0035] Advantageously, the wetting agent also prevents or significantlydelays the precursor caking.

[0036] The proportion of wetting agent in the precursor is typicallybetween about 1 and 5% by weight, and is preferably between 2 and 4% byweight for precursors in the form of a slip or a slurry and between 2and 5% by weight for precursors in the form of a paste.

[0037] The so-called calcination heat treatment comprises at least onestep at a high temperature, typically between 650 and 1300° C., and moretypically between 800 and 1300° C., capable of transforming the greenlayer into a refractory ceramic, that is advantageously in the vitreousstate. The composition of the vitreous phase typically comprises between5 and 25% by weight of silica obtained from the resin (the remainder,typically 75 to 95% by weight, consists essentially of the mineralfiller). The calcination temperature also depends on the substrate; forexample, in the case of a metallic substrate, it is advantageously lessthan the softening temperature of the substrate. Furthermore, it is alsopreferable to use a calcination temperature greater than the workingtemperature of the coated substrate. The heat treatment may include anintermediate step at a temperature of between 200 and 600° C. (typicallybetween 200 and 250° C.). This intermediate step is preferably capableof causing crosslinking of the resin, and possibly decomposition of theresin, before “ceramisation”(or final calcination) of the coating. Inthis case, it is possible, according to an advantageous variant of theinvention, to continue in situ calcination heat treatment, in otherwords when using the substrate at high temperature (advantageouslyhigher than 650° C.).

[0038] The duration of the heat treatment is advantageously such that itenables complete ceramisation of the precursor. The temperature increaseis preferably sufficiently slow to prevent the coating from cracking.

[0039] During the heat treatment, the organic compounds are eliminated(by evaporation and/or by decomposition) leaving a refractory solid on asurface of the substrate. For example, this solid may be formed frommetal originating from the metal compound and silicon originating fromthe silicone resin. In the case of alumina, silanol groups Si—OH of thepolysiloxane seem to create covalent links with the OH groups ofalumina, the said links seem to transform into Si—O—Al links withrelease of water, during the heat treatment to form an aluminosilicate,which is advantageously in the vitreous state. A similar mechanism mayoccur with metal compounds other than alumina.

[0040] The ambient atmosphere during the calcination treatment isadvantageously non-oxidizing, particularly to prevent oxidation of thesubstrate at the substrate-coating interface that could cause decohesionbetween the substrate and the coating, or possibly destruction of thesubstrate (for example when the substrate is made of graphite).

[0041] The final coating may comprise two or more successive layers thatmay be applied by coatings and successive heat treatments, i.e. bysuccessive coating/heat treatment sequences. In other words, the layercoating and calcination treatment operations are repeated for eachelementary layer in the final coating. The successive layers may have adifferent composition, such that they have different chemical andmechanical properties. This variant provides a means of adapting eachlayer to a local function, such as bond to the substrate for the firstlayer, mechanical strength for intermediate layers and chemicalresistance for the surface layer.

[0042] Another object of the invention is a substrate in which at leastpart of the surface comprises at least one refractory layer obtainedusing the said precursor or using the said coating method, the saidrefractory layer being advantageously in the vitreous state, with orwithout a gradient of the composition in the direction perpendicular tothe surface of the substrate.

[0043] Another object of the invention is the use of the said precursoror the said coating method for the protection of a substrate,particularly for the protection of a material and/or a piece ofequipment that will be exposed to an oxidising environment, or liquidmetal (particularly aluminium, an aluminium alloy, magnesium or amagnesium alloy, in the liquid state) and/or a solid or molten salt.

[0044] The term “substrate” must be understood in the broad sense: thesubstrate may be made of metal (such as an iron-nickel-chromium basedalloy (typically a steel or inconel)), or a refractory material or acarbonaceous material (such as graphite), or a mixture or a combinationthereof; it may be a particular object (typically a piece of equipment,such as a metallic or refractory component of a casting unit, a nozzle,a liquid metal distributor in a sump, a screen made of steel(particularly stainless steel) or a refractory or ceramic material, ametallic or refractory filter, a liquid metal or gas bubbles injector, arotor, a scraper, a pouring spout, an ultrasound sensor, a measurementsensor (ultrasound, temperature, etc.) designed to be immersed in liquidmetal, parts made of carbonaceous materials, bricks made of graphite,etc.), or a material, particularly a coating material (such as a brickmade of a refractory material or a carbonaceous material (such asgraphite). The substrate may be porous or non-porous.

[0045] Tests

[0046] Several tests have been carried out on different substrates.These tests were carried out using the following components:

[0047] Mineral Fillers:

[0048] a calcined alpha alumina powder (technical alumina ref. P172SBmade by the Aluminium Pechiney company) with a D50 of 0.5 μm and a BETspecific surface area of 6 to 8 m²/g. The alumina was finely ground(size grading typically between 0.2 μm and 1.5 μm);

[0049] a ZrO₂ powder (Saint Gobain reference CSO2) with a D50 of 0.8 μmand a BET of 5.5 m²/g;

[0050] a TiO₂ powder (Kemira reference UV Titan P 370), with a grainsize of 0.06 μm;

[0051] a TiB₂ powder (reference Metabap 143) with a D50 of 1.7 μm;

[0052] Silicone resin: a MK polymethylsiloxane made by the Wackercompany, which is a trifunctional resin with about 1% of OH groups. Thisresin was composed of about 80% of silica equivalent and 20% of methylgroups, which dissociate at a temperature of the order of 450° C.;

[0053] Organic solvent: xylene;

[0054] Wetting agent: a Dynasylan® 4140 polysilane made by theDégussa-Hüls company (about 3% by weight compared with the quantity ofmetal compound in all cases).

[0055] Series of Tests with Slip

[0056] Several slip compositions were tested. They had the compositionsgiven in table I (% by weight). The proportions were such that therefractory coating obtained comprised about 80% by metal compoundequivalent weight (or mixture of metal compounds) and 20% by silicaequivalent weight. The concentration of silicone resin in the xylene wasabout 250 g/l. TABLE I Component No. 1 No. 2 No. 3 No. 4 No. 5 No. 6Alumina 44.9 — — 35.9 — — (Al₂O₃) Zirconia — 44.9 — — — — (ZrO₂)Titanium — — 30.2 — — — oxide (TiO₂) Titanium — — — 9 44.9 66.0 diboride(TiB₂) Silicone 14 14 9.4 14 14 11.2 resin Organic 39.8 39.8 59.4 39.839.8 22.8 solvent Wetting 1.35 1.35 0.9 1.35 1.35 — agent

[0057] Xylene was mixed so as to obtain a homogeneous mixture. Thesilicone resin was dissolved at ambient temperature in this organicsolvent until a homogeneous solution was obtained. If necessary, thewetting agent was then added to this solution. After a 10 minute ageingtime, the filler was added to this solution and mixed (by stirring) soas to obtain a homogeneous slurry.

[0058] Several tests were carried out on a 304 L stainless steel grid,as a substrate. The diameter of the wires on this grid was 100 μm andthe mesh size was 200 μm.

[0059] The substrate was previously cleaned using a solvent capable ofdegreasing surfaces, particularly acetone. In some tests, the grid wasalso dipped in a caustic soda solution (for example 60 g/l at ambienttemperature).

[0060] The slip was deposited in a thin layer on the substrate bypainting (using a brush and a roller so as to open up the meshes). Thecoated substrate was then left in the open air for a few minutes so thatthe solvent could evaporate. It was then found that the layer driedquickly and that the deposition bonded firmly to the substrate (thedeposition was very hard and uniform, and the grid could easily behandled). The percent of blocked meshes was small (typically less than10%). After the drying operation, the substrate coated with slip washeat treated for one hour at a temperature of 900° C.

[0061] Typically, the coating was obtained by deposition and baking offour thin and successive uniform layers. Excess precursors in eachdeposition were removed so as to prevent the occurrence of bond defects.The final thickness of the coating was typically of the order of 50 μm.This coating was very uniform and strong (with good cohesiveness andnon-powdering) and did not block up the grid openings (the mesh size wasreduced only to about 100 μm).

[0062] The grids thus coated were dipped in liquid aluminium for twohours at a temperature of between 700 and 800° C. This test did not showup any deterioration to the coating.

[0063] Grids thus coated were used to filter liquid aluminium. This testshowed that these grids enable circulation of liquid aluminium withoutany excessive pressure loss and without damage to the coating. Theresults obtained for initial flows on an area of the order of 13 cm² areshown in table II.

[0064] These results show that the metal flow is high with all testedslips. TABLE II Slip No. 1 No. 2 No. 3 No. 4 No. 5 Initial flow 0.0110.017 0.045 0.05 0.19 (kg/s)

[0065] The few tests carried out with a slip similar to slip No. 5, butwithout a wetting agent, gave results similar to those obtained withslip No. 5. Slip No. 6 gave flows similar to those obtained with slipsNo. 1 to 5.

[0066] Series of Tests with Paste

[0067] A paste composition was tested. Its composition was (% byweight): 82% of mineral filler (alumina), 13.9% of silicone resin and4.1% of organic solvent. The proportions were such that the refractorycoating obtained comprised about 80% of metal compound equivalent weight(or a mixture of metal compounds) and 20% by silica equivalent weight.The compositions did not include any wetting agent.

[0068] The paste obtained was deposited on a metallic substrate (a thinstrip) made of 304 L stainless steel using a spatula.

[0069] After the drying operation, the coated substrate was cross-linkedat a temperature of 240° C. for one hour and was then baked at atemperature of 800° C.

[0070] The final thickness of the coating was typically of the order of200 to 300 μm. This coating was very uniform and strong (with goodcohesiveness and non-powdering).

1. Coating precursor comprising a silicone resin, a mineral filler andan organic solvent capable of dissolving the said resin and putting themineral filler into suspension, the silicone resin and the mineralfiller being capable of chemically reacting so as to produce a solidlayer on a substrate after the organic solvent has evaporated and acohesive refractory layer after a calcination operation.
 2. Coatingprecursor according to claim 1, characterised in that the siloxanicpatterns of the silicone resin include trifunctional or quadrifunctionalpatterns.
 3. Coating precursor according to claim 1 or 2, characterisedin that the silicone resin is a polysiloxane comprising a proportion ofOH groups.
 4. Coating precursor according to claim 3, characterised inthat the said polysiloxane is a polymethylsiloxane, apolydimethylsiloxane, a polymethylsilsesquioxane, or a mixture thereof,comprising a proportion of OH groups substituted for methyl groups. 5.Coating precursor according to claim 3 or 4, characterised in that theproportion of OH groups is between about 0.5% and about 2%.
 6. Coatingprecursor according to any one of claims 1 to 5, characterised in thatthe said organic solvent is apolar.
 7. Precursor according to claim 6,characterised in that the apolar organic solvent is a xylene or atoluene.
 8. Coating precursor according to any one of claims 1 to 7,characterised in that the mineral filler is chosen from among metaloxides, metal and non-metal carbides, metal and non-metal borides andmetal and non-metal nitrides, or a combination or a mixture thereof. 9.Coating precursor according to claim 8, characterised in that themineral filler comprises a calcined alpha alumina.
 10. Coating precursoraccording to claim 8 or 9, characterised in that the mineral filler ischosen from the group comprising ZrO₂, ZrB₂, TiB₂, TiO₂, boron nitride,and a mixture or a combination thereof.
 11. Coating precursor accordingto any one of claims 1 to 10, characterised in that the mineral filleris in the form of a powder with the size of the grains between 0.05 umand 50 um.
 12. Coating precursor according to any one of claims 1 to 11,characterised in that the said coating precursor also contains a wettingagent capable of facilitating the formation of a thin layer.
 13. Coatingprecursor according to claim 12, characterised in that the said wettingagent is a silane polyether.
 14. Coating precursor according to eitherclaim 12 or 13, characterised in that the proportion of wetting agent inthe precursor is between 1 and 5% by weight.
 15. Precursor according toany one of claims 1 to 14, characterised in that it is in the form of aslurry or a slip.
 16. Precursor according to claim 15, characterised inthat the proportion of solvent in the precursor is between 7.5% and 60%by weight.
 17. Precursor according to claim 15,. characterised in thatthe proportion of solvent in the precursor is between 15% and 30% byweight.
 18. Coating precursor according to any one of claims 15 to 17,characterised in that the proportion of silicone resin in the precursoris between 5 and 30% by weight.
 19. Coating precursor according to anyone of claims 15 to 17, characterised in that the proportion of siliconeresin in the precursor is between 7.5 and 20% by weight.
 20. Precursoraccording to any one of claims 15 to 19, characterised in that theproportion of mineral filler in the precursor is between 30% and 75% byweight.
 21. Precursor according to any one of claims 15 to 19,characterised in that the proportion of mineral filler in the precursoris between 45% and 70% by weight.
 22. Precursor according to any one ofclaims 1 to 14, characterised in that it is in the form of a paste.
 1923. Precursor according to claim 22, characterised in that theproportion of solvent in the precursor is between 2.5% and 10% byweight.
 24. Precursor according to claim 22, characterised in that theproportion of solvent in the precursor is between 10% and 17.5% byweight.
 25. Coating precursor according to any one of claims 22 to 24,characterised in that the proportion of silicone resin in the precursoris between 7.5 and 20% by weight.
 26. Coating precursor according to anyone of claims 22 to 24, characterised in that the proportion of siliconeresin in the precursor is between 10 and 17.5% by weight.
 27. Precursoraccording to any one of claims 22 to 26, characterised in that theproportion of mineral filler in the precursor is between 70% and 95% byweight.
 28. Precursor according to any one of claims 22 to 26,characterised in that the proportion of mineral filler in the precursoris between 75% and 90% by weight.
 29. Precursor according to any one ofclaims 22 to 28, characterised in that it also includes an additivecapable of reducing the viscosity of the precursor.
 30. Precursoraccording to claim 29, characterised in that the additive comprises adispersing agent such as a stearic acid. 20
 31. Precursor according toclaim 29 or 30, characterised in that the proportion of additive in theprecursor is less than 2% by weight.
 32. Precursor according to claim 30or 31, characterised in that the proportion of additive in the precursoris between 0.1 and 1% by weight.
 33. Method for coating a given surfaceof a substrate with at least one refractory layer containing siliconwherein: - the said surface is coated with a coating precursor accordingto any one of claims 1 to 21, so as to form a green layer; - a heattreatment called calcination treatment is carried out to eliminatevolatile materials, to calcine the said green layer and to form acohesive refractory layer.
 34. Method according to claim 33, whereincoating is deposited by brushing, by dipping or by atomisation. 35.Method for coating a given surface of a substrate with at least onerefractory layer containing silicon wherein: - the said surface iscoated with a coating precursor according to,any one of claims 22 to 32,so as to form a green layer; - a heat treatment called calcinationtreatment is carried out to eliminate volatile materials, to calcine thesaid green layer and to form a cohesive refractory layer.
 36. Methodaccording to claim 35, wherein coating is deposited by spraying. 21 37.Method according to any one of claims 33 to 36, wherein the temperatureof the substrate is increased above the ambient temperature beforecoating.
 38. Method according to any one of claims 33 to 37, wherein thesaid calcination treatment comprises at least one step at a temperatureof between 650 and 1300° C capable of transforming the green layer intoa refractory ceramic.
 39. Method according to any one of claims 33 to38, wherein the said heat treatment comprises an intermediate step at atemperature of between 200 and 600° C.
 40. Method according to any oneof claims 33 to 39, wherein the said calcination treatment is carriedout in a non-oxidising atmosphere.
 41. Method according to any one ofclaims 33 to 40, wherein the said refractory layer is formed fromseveral successive layers.
 42. Method according to any one of claims 33to 41, characterised in that the said substrate is made of metal, arefractory material or a carbonaceous material, or a mixture or acombination thereof.
 43. Method according to claim 42, characterised inthat the said metal is an iron - nickel - chromium based alloy. 44.Method according to any one of claims 33 to 41, wherein the saidsubstrate is chosen from the group comprising metallic or refractorycomponents of a casting unit, nozzles, liquid metal distributors in asump, screens made of steel, 22 stainless steel, a refractory materialor ceramic, metallic filters, refractory filters, liquid metalinjectors, gas bubble injectors, rotors, scrapers, pouring spouts,ultrasound sensors, measurement sensors designed to be immersed inliquid metal,. bricks made of refractory material, parts made ofcarbonaceous materials and bricks made of graphite.
 45. Use of theprecursor according to any one of claims 1 to 32 or of the methodaccording to any one of claims 33 to 41 for the protection of a materialand/or a piece of equipment that will be exposed to an oxidisingenvironment, or liquid metal and/or a solid or molten salt.
 46. Useaccording to claim 45, characterised in that the said material is ametal, a refractory or a carbonaceous material, or a mixture or acombination thereof.
 47. Use according to claim 46, characterised inthat the said metal is an iron - nickel - chromium based alloy.
 48. Useaccording to claim 45, characterised in that the said part is chosenfrom the group comprising metallic or refractory components of a castingunit, nozzles, liquid metal distributors in a sump, screens made ofsteel, stainless steel, a refractory material or ceramic, metallicfilters, refractory filters, liquid metal injectors, gas bubbleinjectors, rotors, scrapers, pouring spouts, ultrasound sensors,measurement sensors designed to be immersed in liquid metal, bricks madeof 23 refractory material, parts made of carbonaceous materials andbricks made of graphite.
 49. Substrate characterised in that at leastpart of the surface comprises at least one refractory layer obtainedusing a precursor according to any one of claims 1 to 32 or using themethod according to any one of claims 33 to
 41. 50. Substrate accordingto claim 49, characterised in that it is made of metal, a refractorymaterial or a carbonaceous material, or a mixture or a combinationthereof.
 51. Substrate according to claim 50, characterised in that thesaid metal is an iron - nickel - chromium based alloy.
 52. Substrateaccording to claim 49, characterised in that it is chosen from among thegroup comprising metallic or refractory components of a casting unit,nozzles, liquid metal distributors in a sump, screens made of steel,stainless steel, a refractory material or ceramic, metallic filters,refractory filters, liquid metal injectors, gas bubble injectors,rotors, scrapers, pouring spouts, ultrasound sensors, measurementsensors designed to be immersed in liquid metal, bricks made ofrefractory material, parts made of carbonaceous materials and bricksmade of graphite.